Light-emitting diodes (LEDs) are widely used as loads in various applications, such as landscape lighting, street lighting, backlighting for electronic products, etc., due to characteristics of energy-savings, high efficiency, and low cost, as compared to other lighting options. Typical LED driving power supplies are designed to be input by commercial power, and to provide DC current for LEDs by rectifying the commercial power to DC power, and then performing a step-up or step-down conversion to the DC power.